Earth at seven billion

In an era of high anxiety, few issues rattled people in the 1960s and 1970s more than the Earth’s seemingly runaway population growth. The sense of imminent overcrowding doom was chillingly articulated by Paul Ehrlich, the Stanford University biologist whose 1968 book, The Population Bomb, became an unlikely bestseller, propelled in part by the academic’s numerous appearances on Johnny Carson’s Tonight Show. The swelling ranks of humankind would lead to “hundreds of millions” dying of starvation by the 1970s, a substantial increase in the global death rate and assorted ecological disasters, he predicted. Involuntary sterilization might be needed to lessen the coming cataclysm.

“We can no longer afford merely to treat the symptoms of the cancer of population growth; the cancer itself must be cut out,” he wrote. Four decades later, the Earth’s population has doubled and the United Nations predicts a newborn’s arrival some time this fall will push the total to seven billion souls.

By 2050, another two billion humans are likely to be jostling for elbow room. Yet the doomsaying predictions of Prof. Ehrlich and others have in most cases failed to materialize. The world still has more than its share of misery: Almost one billion people go hungry every day and 1.4 billion live in extreme poverty. But as the population expanded at a pace never seen before, the overall death rate dropped rapidly, life expectancy climbed and the number in poverty — though still huge — shrank.

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Tens of millions moved into the middle class in China, southeast Asia and India.

“Every indicator of human well-being that you can measure … there’s no question it’s better today, no matter how many people we have,” said Hania Zlotnik, head of the UN’s population division.

“On the whole, society has been extremely successful, both in reducing population growth from its peak and making life better for most people.”

Since The Population Bomb exploded in the late 1960s, the Green Revolution has made agriculture exponentially more productive, feeding billions more, while economies that were near collapse are now thriving. Meanwhile, many demographers predict the population size will not keep spiralling out into “oblivion,” as Prof. Ehrlich suggested, but level off by the end of this century.

“In the end, it’s always the same story,” said Pierre Desrochers, a geography professor at the University of Toronto. “People forget that human beings are not just mouths that eat, but brains to work out new solutions.”

Still, experts warn there is no reason to be complacent — the number of humans keeps expanding and those average improvements in well-being obscure pockets of calamity. Many parts of the world — sub-Saharan Africa most prominent among them — still have high fertility rates and widespread, grinding poverty.

“The problems are here and now,” said Joel Cohen, head of the laboratory of populations at New York’s Rockefeller University. “People forget there are a billion chronically hungry people; every day those people wake up and they’re hungry all day, and they go to sleep hungry.”

And if their moribund economies do take off — as everyone hopes — they could add to climate change and other worrying environmental problems, originally the product of the developed world.

As it turns out, population expansion is not just a simple question of reproduction run amok, but a subtle interplay between death rates, birth rates and economics.

For much of human history, population levels changed little, says Frank Trovato, a sociology professor and population expert at the University of Alberta. While women had many babies, their fecundity barely kept pace with mortality rates fuelled by disease, hunger and war.

By the mid 18th-century, though, cities and towns in Europe, at least, were becoming increasingly crowded and dirty, health improved, food became more abundant and the population started to increase. Later improvements in public health — like sewers that separated disease-ridden human waste from drinking water — kept people alive even longer, while the Industrial Revolution raised general well-being.

History indicates that as life expectancy increases and more children survive into adulthood, birth rates decline.

There is always a gap, though — called a demographic transition — before fertility slows enough to tally with the rising longevity. When it does, couples have enough children at most to replace themselves. During the transition period, however, the numbers rocket up.

By the 1960s, fertility rates had dropped to near-replacement levels in the industrialized world, but remained higher elsewhere. World population, only one billion in 1800, climbed to two billion by 1927, three billion by 1959, four billion by 1974 and six billion by 1998, according to UN figures.

The number is projected to tick over to seven billion some time around Oct. 31, with the milestone baby more likely to be born in India than in any other country.

Fears about population growth date back centuries, suggesting an almost innate human anxiety about the effects of too many human beings.

Prof. Desrochers points to the early Christian theologian Tertullian, who argued 1,800 years ago the world’s “teeming population” was overly burdensome, and pestilence, conflict and other deadly events were a useful “remedy” to prune the overgrowth.

Much later, at the end of the 18th century, Thomas Malthus, an English clergyman and scholar, theorized population expansion would inevitably outpace society’s ability to feed itself, meaning famine and disease would sooner or later bring the boom to a halt.

Neo-Malthusians expanded on and popularized his ideas in the mid-1900s. The notion picked up steam in the popular media, with Time magazine featuring the “Population Explosion” on a cover in 1960. Even pop culture joined in. The movie Soylent Green imagined a dystopic, over-populated future where authorities feed the masses a mysterious substance that turns out to be made from other people, sacrificed for the common good when they get old.

Prof. Ehrlich’s book, commissioned by the Sierra Club, likely had the biggest impact on public consciousness, with its predictions of mass starvation and resource depletion. On the face of it, he at least overstated his case.

With twice as many people on Earth, global average death rates have dropped to eight per 1,000 per year, from 13 in 1970. Life expectancy has soared from 56 years to 67. The number living in extreme poverty slid to 1.4 billion in 2005 from 1.8 billion in 1990. And the percentage of people who are malnourished has halved, though the total number has climbed — from 815 to 925 million — over the same period.

Even as Prof. Ehrlich predicted Mexico would be unable to feed itself, new, Green Revolution strains of wheat were turning it from a net importer to a net exporter of the grain. Those farming innovations later helped transform crop yields in Asia.

“Science has progressed in many ways in parallel with population growth,” said Prof. Trovato.

Economic reversals have meanwhile raised living standards in much of east Asia, parts of India and Latin America.

Fertility rates are also dropping to below the replacement level of two children in much of the industrialized world and in emerging economies such as Brazil and China. Other regions are hovering just above that level, while a third group, mainly in sub-Saharan Africa and south Asia, still has birth rates as high as four or five.

If fertility remained at those levels, the population explosion would go ballistic, pushing the numbers to 15 billion by 2100, says the UN’s population division. Conversely, if dramatic advances were made in lowering birth rates now, the numbers of humans could actually start to decline by the late 2000s.

The agency is placing its bets on a middle projection, where fertility is curbed slowly, resulting in nine billion by 2050 and more than 10 billion by the end of the 2000s, before levelling off.

In some ways, Prof. Ehrlich and other neo-Malthusians may have got it right. The limits on fertility and increases in food production they urgently recommended have been key to helping the world cope with, and even thrive, amid the population explosion.

With one billion people undernourished already, however, and another two billion coming soon — mostly in the countries least equipped to absorb them — the challenges remain immense.

Feeding them all will likely require another Green Revolution, as the novel crop varieties that boosted yields in Latin America and Asia do not work in sub-Saharan Africa, where irrigation is scarce and food production a fraction of that on farms elsewhere.

A 2008 report by the UN’s Food & Agriculture Organization says feeding nine billion people by 2050 can be done, but would require annual private and public investments of US$83-billion on developing-world agriculture.

Even now, enough grain is produced globally to feed 11 billion mouths, said Prof. Cohen. The problem is a third is eaten by cows, pigs and other livestock — helping sate the rich world’s craving for meat— and a sixth is used for fuel, other industrial applications and seed.

He advocates an end to U.S. farm subsidies that divert much of the country’s corn crop to ethanol production. “The world chooses to feed its machines and its domestic animals before it feeds its people,” he laments.

The famine now ravaging Somalia raises another key issue. Hunger often has more to do with political and climatic factors than the sheer number of people, and solving problems like deep-rooted corruption might be a precursor to more tangible agricultural advance.

“Consider the Horn of Africa. Is this sustainable?” said Don Kerr, a social demographer at King’s College, University of Western Ontario. “It continues to experience famine due to a drought and political and economic mismanagement.”

At the same time, more efforts are needed to lower the birth rate in high-fertility regions to avoid worst-case population scenarios, and potentially to slow growth even more than expected, said Ms. Zlotnik.

The UN population czar rejects the conventional economic wisdom that fertility starts falling only as affluence in a country rises, saying there are many examples where birth rates have shrunk independent of an economic boom. Bangladesh, for instance, is moving fast toward replacement-level fertility because of robust programs that encourage child and maternal health and family planning.

Yet surveys of women in the developing world suggest 215 million would like access to birth control but cannot get it.

There are some activists who still voice existential fears for the future. Lester Brown, founder of the environmental group Worldwatch Institute, says population growth, coupled with climate change, threatens to bring an end to global civilization unless corrective measures are urgently taken.

In 2009, Prof. Ehrlich conceded he may have overblown the hunger problem, not foreseeing the impact of the Green Revolution. But he argued he was overoptimistic in other areas, failing to predict climate change, widespread deforestation and damage to the Earth’s ozone layer, and believes population-related problems have only got worse.

Still, a deep-seated fear of the bomb seems to have dissipated. It has been replaced with a sense solutions are at hand, but action is overdue to rectify the problems of the current seven billion — and those to come.

“When one looks at the broad picture of human history… it’s been a history of population meeting challenges that come up,” said Prof. Trovato.

“I think we will continue in this way … but that doesn’t necessarily mean that all parts of the world will be equal in meeting the challenges.”

Confucius (551- c. 479 BC)
A disciple asked, “Once there are so many people, what should be done?” “Enrich them,” said the Master. “Once they are enriched, what next?” “Educate them.”

Plato (429-347 BC)
“Fear of poverty and war will make them keep their family within their means.”

Artistotle (384-322 BC)
“A great city is not to be confounded with a populous one.”

Tertullian (c. 160- c. 220)
“Pestilence, and famine, and wars, and earthquakes have to be regarded as a remedy for nations, as the means of pruning the luxuriance of the human race.”

Richard Hakluyt (1527-1616)
“[T]hrough long peace and seldome sickness … we are growen more populous than ever heretofore; … many thousandes of idle persons are within this realme, which, havinge no way to be sett on worke, be either mutinous and seeks alteration in the state, or at leaste very burdensome to the commonwealthe.”

Thomas Malthus (1766-1834)
“[There is a] constant effort towards an increase in population [which tends to] subject the lower classes of society to distress and to prevent any great permanent amelioration of their condition.”

Paul Ehrlich
“Population will inevitably and completely outstrip whatever small increases in food supplies we make … The death rate will increase until at least 100-200 million people per year will be starving to death during the next 10 years.”

Donella and Dennis Meadows
The Earth is finite. Growth of anything physical, including the human population and its cars and buildings and smokestacks, cannot continue forever.”